St. Augustine Grass Lawn Care Plan

St. Augustine Grass Profile

St. Augustine grass (Stenotaphrum secundatum) is the dominant lawn grass across Florida, the Gulf Coast, and lower Texas. It is the most shade-tolerant warm-season grass available, spreading aggressively through stolons to form a dense, weed-suppressive lawn that handles the hot, humid conditions of the Deep South better than any alternative.

St. Augustine cannot be established from seed — it is only available as sod or plugs, which means initial establishment costs are higher than seeded alternatives. But in its preferred climate zone, nothing outperforms it for overall performance across a range of sun and shade conditions.

• Active growth: Year-round in South Florida; spring through fall in North Florida and Gulf Coast
• Shade tolerance: Outstanding — the best of any warm-season grass
• Drought tolerance: Moderate — requires more irrigation than Bermuda or Zoysia
• Key pest: Chinch bugs — the most damaging pest for St. Augustine in Florida
• Establishment: Sod or plugs only — no viable seed available for residential use

Mowing: Height and Frequency

St. Augustine should be mowed at 2.5–4 inches, significantly taller than Bermuda or Zoysia. The taller height maintains the health and density of the large leaf blades that characterize St. Augustine. Cutting below 2 inches weakens the lawn and invites weed invasion and chinch bug damage.

In full sun, maintain 2.5–3 inches. In shade, raise to 3.5–4 inches to compensate for reduced photosynthesis. A standard rotary mower is appropriate for St. Augustine at its target heights — the coarser blade structure does not require the precision cut of a reel mower the way Bermuda does.

Keep rotary mower blades sharp. Dull blades on the large, coarse St. Augustine leaf produce ragged, discolored cuts that invite fungal disease entry in the humid Gulf Coast climate. Sharpen blades every 25–30 hours of use or at least once per season.

Fertilizing Schedule

St. Augustine has moderate-to-high nitrogen requirements during the growing season. Iron deficiency, visible as yellowing between leaf veins while the veins themselves stay green, is one of the most common problems in Florida St. Augustine lawns and is often caused by high soil pH locking out iron uptake.

• Growing season feeding: Apply fertilizer every 6–8 weeks when grass is actively growing. In South Florida, this can mean year-round feeding on a reduced schedule. In North Florida and the Gulf Coast, suspend fertilizing November through February.
• Milorganite for summer: Milorganite is the safest summer fertilizer for St. Augustine — organic-based, burn-proof in heat, and effective at building overall soil health alongside turf fertility.
• Iron supplementation: If yellowing appears between leaf veins, apply a liquid iron product as a foliar spray. Iron deficiency often indicates high soil pH — test and correct to 6.0–7.0.
• Florida phosphorus restrictions: Many Florida counties restrict phosphorus fertilizer application due to water quality concerns. Check local ordinances before purchasing any fertilizer — a zero-phosphorus formula may be required.

Weed Control and Chinch Bug Management

St. Augustine density makes it naturally competitive against most weeds when properly maintained. However, it is sensitive to some herbicides that are safe on other warm-season grasses, so label-reading is essential before any application.

Spring pre-emergent: Apply Prodiamine 65 WDG before soil temps hit 55°F. Safe for established St. Augustine at label rates. Provides season-long crabgrass and annual weed protection from a single application.

Chinch bug identification and control: Chinch bugs are the most destructive pest for St. Augustine in Florida. They appear as irregular brown patches that do not respond to irrigation — damage resembles drought stress but worsens as watering increases. To confirm, push a coffee can with the bottom removed into the soil at the edge of a damaged area and fill with water. Chinch bugs float to the surface within two to three minutes if present. Treat confirmed infestations with a bifenthrin-based insecticide applied at the edges of active damage areas.

Large patch fungal disease: In fall and spring when temperatures are cool and humidity is high, St. Augustine is vulnerable to large patch (Rhizoctonia solani), which appears as expanding circular brown areas. Apply a labeled fungicide at the first sign of symptoms in September or when soil temps drop below 70°F in fall.

Seasonal Care Overview

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